Ghost Keyframes - Missing Keyframes that are still working?
that happens , with me also  ,actually thats not a problem with blender or the ad-don , its with you , you probably are not selection the correct object in your animation  you are selecting an object that doesn't have a key frame there , try selection all things and look if there is something having a key frame there and try deleting it , or you can also make a fresh keyfram there